1. Field of the Invention
The present invention relates to a tomographic imaging apparatus, and more particularly, to a tomographic imaging apparatus and a photographing method that use optical coherence tomography that is used for observation of a fundus and the like.
2. Description of the Related Art
A photographing apparatus using optical coherence tomography (OCT) in which interference due to low coherent light is utilized (hereinafter, also referred to as OCT apparatus) is now put into practical use. The photographing apparatus is capable of acquiring a tomographic image at a resolution that substantially corresponds to the wavelength of light entering an object to be inspected, which thus leads to high-resolution photographing of a tomographic image of the object.
In an OCT apparatus, light from a light source is split into measuring light and reference light by a beam splitter or the like. The measuring light irradiates an object to be inspected, such as an eye, via a measuring light path. Then, return light from the object to be inspected is combined with reference light and is guided to a detector as interfering light via a detection optical path. Here, the return light refers to reflected light and scattered light including information about an interface in the light-irradiation direction with respect to the object to be inspected. The interfering light of the return light and the reference light is detected by the detector and is analyzed so that a tomographic image of the object to be inspected can be obtained.
The OCT apparatus is used for photographing a tomographic image of a fundus retina in many cases, but there is also known a method of photographing the fundus widely so as to determine an eyeball shape (see Japanese Patent Application Laid-Open No. 2006-122649).
However, the eyeball shape determined in this way is calculated from a tomographic image formed based on a principle of the OCT, and therefore indicates an optical distance including information on a refractive index but does not indicate an actual shape and an actual size.